Here, 'was going to phone' in past continuous is correct because
it is used to indicate uncompleted action in the past (with or without time
reference).
'Am going to phone' in present continuous is incorrect because
it implies an action going on at the time of speaking.
'Have gone to phone' present perfect is incorrect because
it is used to indicate an action which started in the past and has continued up
untill now.
'Will go to phone' in future simple is incorrect because it indicates an action, condition or circumstance which has not taken place as yet.